The Young Scientist Program
Genetics/Genomics Teaching Team
http://medicine.wustl.edu/ysp
Funding by Pfizer Inc.
Gourdomics
Introduction
Gourds have traits that differ from plant to plant, such as color and texture. An individual gourd’s
physical characteristics make up its phenotype. These traits are inherited through genes in specific
locations in the gourd genome. Other DNA sequences, called markers, occur throughout the genome.
All of the DNA is collectively called the genotype. A marker that differs between two gourds is
called polymorphic. If we find a polymorphic marker that is linked to the gene for a trait, then we
can predict the physical characteristics, or phenotype of a gourd by looking only at the DNA
markers or genotype.
Materials
5 gourds varying in binary traits (eg: color, shape, texture, size, neck length)
Five “gels” with six lanes, each showing a particular marker for each gourd and
a “mystery gourd” lane typed for the mystery gourd.
Methods
1. For each gel determine whether the marker is long or short for each gourd.
2. Figure out which trait the marker is associated.
3. Using the linkage information, determine the phenotype of the “mystery
gourd” represented by the sixth lane. Then remove the possible mystery
gourds that don’t have that phenotype.
Suggestions
1. Go over color (gel #1) with the students first.
2. Explain how shorter DNA moves faster in the gel than longer DNA because it
can fit in smaller spaces.
3. Move the gourds with the shorter bands forward to mimic the gel. This will
help in figuring out the trait association.
Discussion Questions
1. It it possible to ever find a “green” gourd that has the marker of a “yellow”
gourd? Why or why not?
2. Talk about how this could be used in forensics like on CSI or court TV.
The Young Scientist Program
Genetics/Genomics Teaching Team
http://medicine.wustl.edu/ysp
Funding by Pfizer Inc.
GEL #
LONGER BAND
SHORTER BAND
TRAIT
1
2
3
4
5
The mystery gourd is ____
Some Definitions
Genotype: The DNA that makes up an organism
Phenotype: Physical appearance/observable characteristics of an organism
Polymorphic Marker: DNA that differs between individuals
Sometimes polymorphic markers are linked with a certain trait (or phenotype). If this is the case,
we can use an organism’s genotype to predict their phenotype.